The present invention relates to a cutting tool assembly having an indexable cutting insert and more particularly to a cutting tool assembly for grooving operations in which the cutting insert is mechanically clamped.
In such cutting tool assemblies the cutting insert is retained in an insert pocket defined between clamping surfaces of upper and lower jaws of the insert holder, generally referred to as clamping and base jaws, respectively. The insert holder can be a one-piece tool, or, the clamping jaw can be a separate member. In both cases, at least one screw is used for forcing the two jaws towards each other for secure retention of the cutting insert.
In order to uniquely determine the axial location of the cutting insert an axial stop is provided in the insert pocket. In some prior art cutting tool assemblies the stop is located on one of the clamping surfaces of the upper and lower clamping jaws. In such cases, the cutting insert has to be designed with an appropriate protrusion or recess, on the corresponding insert clamping abutment surface, for engaging the stop. In other prior art cutting tool assemblies, the stop is located at the rear of the insert pocket and the axial location of the cutting insert is fixed when a section of the rear surface of the cutting insert abuts the stop. This arrangement has two disadvantages. First, it restricts the shape of the rear surface of the cutting insert. For double-ended grooving cutting inserts the rear surface is the non-operative front relief surface. Hence, this arrangement restricts the shape of the front relief surface of the cutting insert. Second, if the end portion of the cutting insert, associated with the operative cutting edge, were to break during a cutting operation, the section of the relief surface which would abut the stop on indexing the cutting insert, may well become damaged, in which case the cutting insert could not be indexed, preventing use of the cutting edge associated with the non-damaged end portion of the cutting insert.
To stabilize the cutting insert in the direction perpendicular to the axial direction, the clamping abutment surfaces of the cutting insert are formed with V-shaped protrusions (or grooves) and the clamping surfaces of the insert holder""s jaws are formed with matching V-shaped grooves (or protrusions). According to some embodiments of such cutting tool assemblies, the cutting inserts have a stop-engaging protrusion (or recess) on one of their clamping abutment surfaces and the insert holders having a corresponding stop-engaging recess (or protrusion) on one of the clamping surfaces of one of their clamping jaws. The presence of such stop-engaging protrusions (or recesses) can be disadvantageous.
It is an object of the present invention to provide a double-ended grooving cutting insert that substantially overcomes the above mentioned disadvantages.
It is also an object of the present invention to provide an insert holder for retaining the above-mentioned grooving cutting insert.
In accordance with the present invention there is provided a cutting insert comprising a central body portion extending between two opposite end portions, each end portion being provided with a cutting edge; the central body portion being provided with upper and lower clamping abutment surfaces with first and second side surfaces extending therebetween; at least one of the first and second side surfaces being provided with an axial location member.
In accordance with one embodiment, the axial location member is a protrusion.
Generally, the protrusion is square shaped.
In accordance with another embodiment of the present invention, the axial location member is a recess.
Preferably, the upper and lower clamping abutment surfaces are sloped, defining therebetween a variable distance, so that when the cutting insert is viewed in an end view the distance between the upper and lower clamping abutment surfaces is a maximum at the first side surface and a minimum at the second side surface.
If desired, the upper and lower clamping abutment surfaces have the form of V-shaped protrusions.
Further if desired, the upper and lower clamping abutment surfaces have the form of V-shaped grooves.
There is also provided in accordance with the present invention a cutting tool assembly comprising:
a cutting insert holder; and
a cutting insert;
the cutting insert holder comprising:
an upper clamping jaw having an upper clamping surface;
a lower base jaw having a lower clamping surface;
at least one clamping screw passing through the upper clamping jaw and threadingly connected to the lower base jaw;
an insert holder inner side surface extending between the upper and lower clamping surfaces;
an insert pocket bound on two opposite sides by the upper and lower clamping surfaces and bound on a third side extending between the two opposite sides by the insert holder inner side surface; the insert holder inner side surface being provided with a positioning member;
the cutting insert comprising:
a central body portion extending between two opposite end portions, each end portion being provided with a cutting edge; the central body portion being provided with upper and lower clamping abutment surfaces with first and second side surfaces extending therebetween; at least one of the first and second side surfaces being provided with an axial location member;
wherein the upper clamping abutment surface abuts the upper clamping surface, the lower clamping abutment surface abuts the lower clamping surface and the positioning member engages the axial location member whereby the axial location of the cutting insert is fixed.
In accordance with one embodiment, the axial location member is a protrusion and the positioning member is a rear surface of a recess in the insert holder inner side surface.
Generally, the protrusion is square shaped and the recess has a generally matching square shaped cross section.
In accordance with another embodiment, the axial location member is a recess and the positioning member is a protrusion on the insert holder inner side surface.
Preferably, the upper and lower clamping abutment surfaces are sloped, defining therebetween a variable distance, so that when the cutting insert is viewed in an end view the distance between the upper and lower clamping abutment surfaces is a maximum at the first side surface and a minimum at the second side surface and the upper and lower clamping surfaces of the upper clamping jaw and the lower base jaw, respectively, are matchingly sloped.
If desired, the upper and lower clamping abutment surfaces have the form of V-shaped protrusions and the upper and lower clamping surfaces of the upper clamping jaw and the lower base jaw, respectively, have the form of matching V-shaped grooves.
Further if desired, the upper and lower clamping abutment surfaces have the form of V-shaped grooves and the upper and lower clamping surfaces of the upper clamping jaw and the lower base jaw, respectively, have the form of matching V-shaped protrusions.